The mouse is an important periphery instrument of the computer, and, normally, the positioning pointer of the mouse is using the semi-optical type. As shown in FIG. 1, the structure of the ordinary mouse 10 uses the trackball 11 as the sliding and moving element. One smooth roller 12 of one pivot axle 121 is located in the longitudinal direction of the trackball 11, the other smooth roller 12 of the other pivot axle 121 is located in the latitudinal directions of the trackball 11, and a plurality of toothed wheels 122 are located around peripheries of the two smooth roller 12. There is a distance 123 between two toothed wheels 122, and there are a receiver 21 and a emitter 22 (such as the photo diode and the light emitting diode) respectively located on the circuit board 20 corresponding to both sides of the toothed wheel 122. The trackball 11 slides and moves to make the two pivot axles 121 rotate, and the two rotating pivot axles 121 would make the smooth roller 12 rotate between the receiver 21 and the emitter 22. However, while a light generated from the emitter 22 is incident to a position of the toothed wheel 122, the light would be shielded and the receiver 21 can not receive any light. While the light is incident to the distance 123 between two toothed wheels 122, the receiver 22 can easily receive the light. By shielding and receiving the light, the low level of the signal and the high level of the signal are formed to produce the corresponding coordinate signals of the X and Y axes of the monitor to make the pointer of the mouse 10 on the monitor move with motions of the mouse 10 according to coordinate signals.
However, during the assembly processes of the mouse 10, the all part including electrical elements and opto-electronics of the circuit board 20 are manually inserted, and the total number of the opto-electronics of the aforesaid X and Y axes are four, two for emitter 22 and two for receiver 21. That is, the operator would manually insert the opto-electronics four times, and each one should be inserted in the same angle to make the receiving path and the generating path uniform. However, by using the manually inserted method in enormously producing products the yield is lower and the sensibility of the mouse is degrading. Thus, the coupled way composed by the emitter and the receiver in the real manufacturing line would increase the production hours of product, make the composition of the mouse more difficult, and degrade the yield, so there are improvements needed to improve the aforesaid problems.